The well network was established in three phases (figure 2). The length of the water-quality records (table 1) at the wells vary according to these installation phases.

Phase I consisted of 12 wells in Polk County that were drilled prior to initiation of this project. For the current project, quarterly sampling was initiated at the Phase I wells in April 1999. Most of the Phase I wells were sampled intermittently for agricultural chemicals between 1989 and 1999 by other agencies. Eleven of the Phase I wells were included in the Florida Department of Environmental Protection VISA (Very Intense Study Area) monitoring network in Polk County.
 
Phase II consisted of eleven additional wells drilled during the winter 1999-2000 in Highlands County, the southern part of the study area. Quarterly sampling of the Phase II wells began in April 2000.
 
Phase III includes 8 wells drilled in September 2001 in Polk (5 wells) and Highlands (3 wells) Counties. Sampling of Phase III wells began in October 2001.

 

To prevent contamination of ground water samples, part-per-billions, ‘clean’ sampling protocol is used for sample collection, including the use of teflon tubing to avoid sorbtion of pesticides onto equipment and the use of organic-free water for cleaning equipment before and after sampling. - click to enlarge

Ground-water sampling utilizes mobile lab and digital probes to monitor and record field parameters during well purge. Field parameters must stabilize prior to sample collection. - click to enlarge

Field sampling and probe used to monitor temperature, pH, conductance, and dissolved oxygen content of ground water in the well prior to sampling. - click to enlarge

Target Analytes and
Laboratory Methods